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T O P I C R E V I E W

Headshot

Does anyone know if the exit hatch on Skylab's airlock module, that permitted the astronauts to go EVA, was actually a spare Gemini hatch? It certainly looks like one on page 203 of NASA SP-4208, Living and Working In Space - A History of Skylab. I know that McDonnell built Gemini and McDonnell-Douglas built the airlock module.

From what I have read, I'm almost certain that it isn't a spare Gemini hatch but instead a hatch based on that design. There is a great photo on the history section of the NASA website.

mode1charlie

Interesting that this subject should come up now. I was just at Spacefest, and brought with me a Skylab poster (the one with the cutaway showing astronauts floating inside the modules) to be signed by Bean, Lousma, and Gibson. Lousma was particularly keen to pore over the image, and pointed out for me among other things, the Gemini hatch. I'd never heard this before, but yes, it was basically that. He referred to it as a "Gemini hatch". Whether it was a spare, a modified spare, or a hatch based on the Gemini design I don't know, but it was one of the three.

On edit: someone posted the photo after I started writing my original post, and from the looks of it I'd guess it was one based on the original Gemini design rather than a spare, but not sure.

Various Skylab documentation says it is a Gemini hatch. The airlock module was built in St Louis at the McDonnell plant. The window is a dead give away that it is an actual Gemini hatch. A hatch "based on" the Gemini would have this designed out.

Jay Chladek

It was a Gemini hatch. It underwent some minor modifications, but it was indeed a Gemini hatch.

AAP was under a mandate to use off the shelf technology where they could and some of the engineers lamented that the mandate didn't necessarily speed up their development time or save money as sometimes it can take longer to design a system when you have to use hand me downs as opposed to designing an all new piece of equipment to do a certain job. And longer development tends to lead to cost overruns.

tetrox

In the MSFC "Airlock module final report" it states:

The Gemini hatch used for EVA egress and ingress incorporated a window in the initial design.This window served no functional purpose in the airlock however it was retained to eliminate making a design change.

It goes on to say that a teflon cover was put over the window prior to launch and during SL2 activation a metal cover was put over the inner pane.

This hatch was the same as that used on the Gemini spacecraft. In 1965, Astronaut Edward White had exited through one like it on Gemini 4 to become the first American to walk in space. The hatch had been well tested and proven in space. It was selected because of the predominant design philosophy of Skylab, which was to use, as much as possible, equipment that had proven itself in the environment of space.

Similarly, Figure 81 of Skylab: A Guidebook calls out the "EVA Hatch (Gemini)".

kr4mula

So was this truly a "recycled" hatch leftover from Gemini, or newly manufactured from the Gemini specs?

Headshot

This will be very difficult to nail down, unless some of the original McDonnell engineers/technicians involved with the airlock module read cS and wish to add their two cents.

McDonnell almost certainly had a spare set of Gemini hatches either: (1) in inventory (for emergency replacement during the Gemini Program) or (2) on a high-fidelity mock-up. Remember that NASA chose McDonnell to supply the airlock module in August 1966 (while Gemini was still flying) with the caveat that they would use as much off the shelf Gemini hardware as possible. An existing set of hatches would certainly help.

But, McDonnell probably had not dismantled the Gemini spacecraft manufacturing line at that time of being chosen to manufacture the airlock adapter because they hoped to supply additional Gemini re-entry modules to the Air Force for their MOL program, which was not cancelled until 1969. So McDonnell still had the capability of easily manufacturing Gemini hatches.

On a different tack, can any cS'er verify that each of the 11 flown Gemini re-entry modules have both hatches?

Eleven Gemini returned to Earth. Ten manned (Gemini 3-12) and one unmanned (Gemini 2 which was also re-used as the MOL test article). The boilerplate spacecraft used for Gemini 1 did not survive re-entry.

mikej

quote:Originally posted by Headshot:On a different tack, can any cS'er verify that each of the 11 flown Gemini re-entry modules have both hatches?

I can verify that very few have both hatches:

Gemini 2: Displayed with no hatches

Gemini 3: Displayed with one attached hatch and one hatch nearby

Gemini 4: Displayed at NASM with one attached hatch. The other hatch is displayed at the Cradle of Aviation on Long Island

Gemini 5: Displayed with one attached hatch

Gemini 6: Displayed with one attached hatch

Gemini 7: Displayed with no hatches

Gemini 8: Displayed with one attached hatch

Gemini 9: Displayed with no hatches

Gemini 10: Displayed with no attached hatches, but one nearby

Gemini 12: Displayed with one attached hatch

I have not see Gemini 11, but the Field Guide shows it displayed with only one hatch.

Headshot

Thanks Mike. That list is very interesting.

Comparing it to the National Air and Space Museum's inventory list of human spaceflight artifacts, which lists several Gemini hatches, we cannot determine the location of the following Gemini hatches:

Gemini 2 - 2

Gemini 5 - 1

Gemini 6 - 1

Gemini 8 - 1

Gemini 9 - 1

Gemini 12 - 1

So there are three potential sources for the EVA hatch on Skylab's airlock module:

A reused/refurbished flown Gemini hatch.

A spare unflown Gemini hatch.

A hatch manufactured by McDonnell specifically for the airlock.

This gets worse the deeper we dig into it.

Given the number of unaccounted, flown Gemini hatches, I would have to guess that No. 1 is the most viable, practical and financially desirable source from NASA's point of view. Any other votes?

Robert Pearlman

I've seen it suggested, though not substantiated, that the hatch was already manufactured for MOL and was just re-purposed after that program was shut down.

NASA transferred the Gemini spacecraft to the Smithsonian in 1967 and 1968. Barring information to the contrary, I would assume the flown hatches were no longer available by the time McDonnell would go looking for one for Skylab.

Jim Behling

NASA Technical Memorandum TM X-64810 MSFC Skylab Airlock Module provides some more insight. The AM legacy started with a study for the Spent Stage Experiment Support Module by McDonnell Aircraft in 1965. At that time, it included part of the Gemini Adapter/radiator. 98% of SSESM components were Gemini qualified (must mean non structural components)